Steam turbine power generation plants utilize the energy present in a working medium at high pressure to turn a turbine, which, in turn, turns a generator, generating electrical energy. The working fluid must be free of particulate debris in order to prevent blockages within the system. The chemistry of the working fluid must also be closely monitored and controlled to eliminate harmful soluble contaminants which, if present in the working fluid, may deposit on internal components, possibly damaging those components over time.
During operation of the steam turbine power generation plant the particulate debris may be continually removed from the working fluid via filters etc, and the chemistry of the working fluid may be continually kept within tolerance using continuous treatment techniques such as condensate polishing. However, during periods when the power plant is not operating, such as prior to its first use, or during a scheduled shut down, these contaminants may not be continually removed from the working fluid. If a power plant were to be started-up without regard to a possible build up of these contaminants, the contaminants could overwhelm the continuous treatment techniques in place within the power plant, and cause damage to the components of the power plant.
Techniques for eliminating any built up debris have been developed. One of the simpler methods includes simply generating steam using existing working fluid and possibly adding new, chemically appropriate fluid to the working fluid, exhausting that steam to the atmosphere until the level of particulate debris reaches acceptable limits, and then using that steam to flush the rest of the system until the steam and condensate reach acceptable limits for particulate and chemical contaminants. At that point the working fluid is acceptable for use and the power plant can be brought online. However, this type of purging method may take up to several days, and consume hundreds of thousands of gallons of high quality working fluid.
Some power generation plants are peaking, or ready-reserve power plants, which produce power only during peak demand periods. This requires steam turbine power plants that can come online quickly, as demand changes. Thus, fast start-up times are imperative for such a system. Peaking steam turbine power generation plants, such as the Flex-Plant™ 10 power generation plant, may employ a condenser where the operating pressure in the condenser is above ambient pressure. Conventional methods for treatment of working fluids, such as condensate polishing, may enable a sufficiently fast start-up time in conventional power plants, but in a positive pressure condenser power plant, the associated high temperature of the condensate renders the usual polishing process ineffective. Thus, in order to permit the use of condensate polishing, the condensate must be cooled, which reduces operating efficiency. Consequently, other methods of treating the condensate have been developed.
Positive pressure condenser power plants may inject pressure maintaining fluid, for example nitrogen, or other suitable gas, into the condenser to help maintain positive pressure in the condenser during shutdown, to prevent the entry into the system of contaminant containing atmospheric air during shutdown. A positive pressure condenser system is disclosed in U.S. patent application Ser. No. 12/366,763, filed Feb. 6, 2009, entitled CONDENSER SYSTEM, by James C. Bellows, the entire disclosure of which is incorporated herein by reference. Positive pressure condenser power plants may also use a pressure maintaining fluid, such as a nitrogen blanket, to fill the interior areas of the condenser (Air Cooled Heat Exchanger: “ACHE”), the high pressure boiler, and the main steam system, during periods of shutdown, in order to prevent contaminant containing atmospheric air from entering these components, and subsequently becoming entrained with the working fluid contained in the interior regions of those components. However, the interior of the steam turbine itself and steam exhaust duct between the steam turbine and condenser may not be blanketed with this pressure maintaining fluid so that, for instance, humans may enter and perform required maintenance. Instead, contaminant containing atmospheric air may be left in these interior areas, and an air dryer is used to help minimize moisture and corrosion.